Definition: In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
Input: ['i', 'm', 'r', 'x', '4695', '5129', '7573', 'g']

g, i, m, r, x